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What makes Earth so unique in the Solar System?

Earth is unique in our Solar System most notably because it harbors complex, intelligent life that has survived and evolved through 3.9 billion years of the planet’s 4.5 billion year history. As discussed in Peter Ward and Donald Brownlee's book, "Rare Earth", there are a number of conditions that contribute... More

Why is water so important for life?

Every known form of life on earth, from the largest mammals to the smallest microbes, relies on water. Why? Because water is an extraordinarily versatile molecule - it's the perfect liquid medium in which to dissolve nutrients for ingestion or wastes for excretion, to transport important chemicals or... More

What is the distance between the sun and the asteroid belt?

Astronomers measure distances in our solar system in units of the Earth-Sun distance, which is 150 million kilometers. They call this an astronomical unit or AU. The asteroid belt lies between Mars (1.52 AU) and Jupiter (5.2 AU), with a concentration at about 2.8 AU. Answered by Prof. Lee Kump

Why does the moon change shapes?

The Moon changes shapes because it orbits around the Earth every 28 days, and the fraction that is illuminated by the Sun (and visible on Earth) keeps changing during that time. When the Moon and the Sun are on opposite sides of the Earth, we see a full Moon, i.e., the entire disk... More

What is the currently accepted astrobiology degree plan? If there isn't one yet created; what should my current major and minor consist of? Is there an astrobiology internship developed for aspiring

A few universities are offering advanced degrees in astrobiology--or more accurately, they are providing an opportunity for a specialization in astrobiology while studying for an advanced degree in one of the more traditional disciplines. Four that you might want to look at are Arizona State University, University of California at... More

How does the gravity affect blood circulation, and how could those effects be minimized? I'd like to find some profound scientific information about that. Could you please provide me with some links or articles on that?

Gravity is very important to blood circulation, since the vascular system must work against gravity in order for blood to reach the parts of the body that are higher than the pump (the heart). Animals that walk upright like humans or that have tall necks like giraffes provide a particular challenge for the... More

Can Earth plants grow on Mars?

This question is asked frequently, and now I have some data on which to base a reply. The biggest problems on the surface of Mars are the low temperature and lack of water, and these conditions make it impossible for terrestrial plants to grow there unprotected. But what about plants... More

What is the temperature of Europa (one of Jupiter's moons)?

Like any planet or moon, the temperature depends on where you are. On Europa this can range from as low as -200 C at the surface near the poles to a high in the deep interior that may approach the melting temperature of rocks (above 1000 C). Within its large... More

How long have humans existed on Earth?

Human have existed for roughly half a million years, but this answer depends on the exact definition of "human". Fossil evidence shows that several human-like lineages developed during the past million years or so. >From fossils, the appearance of Homo sapiens is dated at about half a million years, and... More

What comet is currently visible from some spot on earth?

There are always comets visible, but whether you can see them depends on how big a telescope you have. The only recent naked-eye comet was 73P/Schwassmann-Wachmann-3, which was fairly bright in May but can no longer be seen without a telescope. Generally, a comet, if it is visible at all,... More

Is there a planet Nibiru that will pretty much destroy earth in 2012? I watched a video about it last night and I freaked out so bad i was shaking and crying. Is our world coming to an end in 2012? If so... why cant we just blow the thing up and call it a day?

I am really sorry that these crazy Nibiru claims have upset you. I don't want to keep answering these questions about Nibiru, but let me say once more as clearly as I can, for you and the other questioners: Nibiru does not exist. NASA has never discovered or detected Nibiru... More

Nibiru Redux: Six recent questions about Nibiru: (1) I have found a lot of stuff about a so called planet. Planet x or nibiru. It anything they say possible like revolving around the sun clockwise and it has been said that its orbit is way far out past Pluto. Also there are statements that it has a 3600 year orbit around the sun an that is is supposed to return in the near future. Is this possible at all? It sounds fishy to me, but there are supposed pics of it and a lot of scientist talk about it. I even wikipedia searched it. I would just like to find out some info please. (2) Nibiru does exist and I can prove it. Nibiru is in the old testament Exodus 6:4. and you are watching Nibiru from a lab on the south pole. also I have images from a telescope of Nibiru. and people from the southern hemisphere can see Nibiru in the daytime. is that proof enough for you? (3) many signs tell that something big is out there coming and why wouldn't it be true about nibiru / planet x there is a lot of fact historical and scientific but i do understand your awnser but why build a telescope at the south pole an photos and such with this redish dwarf star moving fast in 1983 it was 50 billion miles away and 10 years later it is alot closer is it hiding behind the sun i know you all dont want to start a world wide panic. (4) I read were you said that Nibiru is a hoax. My question to you is why would anyone let the american population know about such a catastrophy? Isnt it the governments job to keep the population at ease? (5) You say Nibiru is a hoax, and no such planet exists, but is Nibiru not Eris? (6) What is this a picture of? http://www.greatdreams.com/nibiru-possible.jpg It's said to be Nibiru, but as you say Nibiru is a hoax. so what is this really a photo of?

I hope this is my last comment on the Nibiru hoax, but questions like the above six keep coming in. Most of the entries on the Internet about Nibiru are false. Wikipedia has it correct when they write that "Nibiru is a name in Sumerian, Babylonian astrology associated with the... More

When most of the planets align in 2012 and planet earth is in the center of the milky way,what will the effects of this be on planet earth? could it cause a pole shift,if so what could we expect.

There is no planet alignment in 2012 or any other time in the next several decades. As to the Earth being in the center of the Milky Way, I don't know what this phrase means, If you are referring to the Milky Way Galaxy, we are rather far toward the... More

Can you please explain the polar shift theory? Supposedly the earth's crust does a 180 degree rotation around the core in a matter of days if not hours. Furthermore, this is stated to be a regular occurrence in Earth's geologic history and has to do with our solar system dipping beneath the galactic equator. Is there any merit to it?

I will try to explain. This is one of the craziest lies that is being promulgated by the 2012 conspiracy theorists -- worse in many ways than the Nibiru hoax. It is totally absurd, and completely untrue, but still the story spreads and is frightening people. First, on the matter of a sudden reversal... More

Solar flares, how dangerous are they? is there evidence of them being dangerous to the earth in the past? I'm always seeing stories on these sites that a major solar flare is coming and it will burn up half the earth. Also is our solar system moving closer together or further apart? For instance, is there any evidence that once in the early days of our solar system that earth was possibly as Venus is now, and Mars was as earth is now.

Solar flares eject high-energy plasma (atomic particles) into space, which could be very dangerous (for a few hours) to any astronauts outside the the Earth's magnetosphere. In the future, astronauts who spend long periods of time on the Moon or traveling to asteroids or to Mars will need protection against occasional large solar flares.... More

Why is it that NASA is being closed or shut down when we are learning far more now about space and what is going on with other planets including the sun?

Fortunately NASA is not being shut down. In fact, both the original budget proposed by the Obama administration and the recent “compromise” budget supported in the U.S. Senate increase NASA’s budget slightly. The discussion in the media over the past to months has not been about the amount of funding... More

I read on the internet that G1.9 is brown dwarf star and also perhaps a supernova remnant. If this is a brown dwarf star, how close is this thing going to get to earth? I read that Spanish artronomers who call themselves the StarViewer Team, claim they discovered a brown dwarf almost twice the size of Jupiter and just beyond our furthest planetoid, Pluto. Although it's not a planet, it appears to have planets or large satellites encircling it. I have a 3 year old son and this article really scares me. Please let me know what this thing is and how close it going to become to earth.

You appear to have fallen for a hoax. The story about a group of Spanish astronomers discovering something twice the size of Jupiter in the solar system just beyond Pluto is pure fiction, without any core of truth. If there were any such object, astronomers would have discovered it decades... More

The Bermuda Triangle and Mexico's Zona De Silencia are on the same latitude and are both mysterious places. From what I understand due to elevated levels of electromagnetism or something. Zona De Silencia is known for pulling meteorites from the sky. The Bermuda Triangle is known for things disappearing. Is it possible that the way Zona De Silencia pulls meteors to the earth it is causing excess gravity that could potentially be used for causing mini worm holes? Why haven't we studied these locations especially zona de silencia with such natural phenomenon?

The facts you state about these locations are simply wrong. No part of Earth "pulls meteorites from the sky", and there are no strange gravity anomalies as you imply; the gravitational field of the Earth is mapped with exquisite precision, partly by companies that use gravity maps to prospect for oil... More

Recently I've heard of a phenomenon that is being observed all around the world. There are instances of prolonged rumbling noises that absolutely cannot be natural. They sound mechanical. I've heard these bizarre rumblings and vibrations, and I'm really worried. I don't know if I should believe that it's part of a pole shift, or some sort of underground tunnel formation. The sound is unnaturally loud and scares the living daylight out of me. Some links where you can hear recordings are http://www.youtube.com/playlist?list=PL7D91B863DD1E5239. AND Why are there suddenly a bunch of strange sounds being heard in the skies around the world? The media is associating this with Dec 21, 2012. I find this very frightening.

I have received several similar questions. I don’t know what the sounds are, and none of my scientific colleagues does either. A quick look at the Internet suggests that many of the reports are from unreliable sites and contain obviously impossible “explanations” such as UFOs, HAARP, Nibiru, pole shifts, or... More

The south pole observatory Nibiru coordinates are: 5, 53, 27, -6, 10, 58; Nibiru Coordinates in Wikisky: 5, 53, 26.78, -6, 11, 0.2; Nibiru Coordinates in Aladin v7.015b: 5 53 26.68 -6 10 58.7. Since the general public are not supposed to know about Nibiru, the area through which it is moving has been blacked out from the Google sky program, but not yet in the Wikisky or Aladin v7.015b programs. Tell me the truth.

This question is misinformed on many fronts (or maybe it is a sick joke). (1) The coordinates given are in the constellation of Orion, near Orion's belt and the Orion Nebula. That part of the sky is easily visible at this time of year from almost the entire Earth. If Nibiru were there... More

How do you prove that something won’t happen? Or prove that something doesn’t exist? I ask, because there seem to be so many people reacting aggressively about this silly Nibiru/2012 Doomsday thing and challenging you to prove that it won't happen or that Nibiru doesn't exist. I've been directing people to your website when they get stressed about the world ending, hope you don't mind.

The logic for proving a negative can be pretty simple: figure out what the implications would be if the proposition were true, and compare those predictions with the facts. Here is an example. (1) If a rogue planet like Nibiru existed and were going to be close to the Earth... More

Isn’t our species having adapted to Earth’s harsh and competitive environment what led us to become sufficiently intelligent, aggressive, and expansive to engage in space travel? Doesn’t it help answer the Fermi Paradox that a species controlling its environments and/or bioengineering new versions of itself to live in new environments, thereby become “comfortable” and loses the very things that led it to be intelligent, aggressive, and expansive?

That is an interesting suggestion. Clearly evolution is favored when there are challenges, even disasters such as mass extinction, to “shake things up”. However, too much environmental stress could have the opposite effect on the biosphere. We have no way of knowing what is the optimum level of stress. And... More

I was just wondering why people seem to slam NASA all the time. You guys (and others) proved and debunked 2012 doomsday, yet people are insisting that your lying and its all a cover up. Why do they think the government is always hiding things from us? So, I believe what you are saying, but sometimes hearing so much of these conspiracy and cover up stories I still wonder if 2012 is the end. Can you 100% say 2012 the world isnt gonna be blown up and doomsday? AND Judging from your website, there are some nutty angry folks out there. But all I want to know from a respected scientist is this: Is anything flying by or hitting earth in 2012 because I need to know if anything is going to hit earth and cause a catastrophe!

Both of you seem to have read my website and other dependable sources of information like Wikipedia and 2012hoax.com, and still you are afraid of something — you don’t know what - destroying the world this year. This is an example of the Big Lie - if a lie is... More

I thank you for all the information! It excites me to learn new things, and it makes me want to keep learning as much as I can. If NASA uses liquid hydrogen and liquid oxygen as fuel, how come no one has designed a vehicle that could run on these to elements? Maybe someone has and I haven't heard about it or maybe it is too expensive? Wouldn't this help the Global Warming predicament?

Power sources that produce electricity by non-explosive combination of hydrogen and oxygen do exist. They are called hydrogen fuel cells or simply fuel cells http://en.wikipedia.org/wiki/Fuel_cell, http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell.htm, http://www.nasa.gov/centers/glenn/technology/fuel_cells.html. NASA has used them to provide electric power for spacecraft for the past half century. You may know... More

Recently I heard on Discovery's news that NASA did find life on Mars about 36 years ago during the viking robot exploration, and that the data was reanalyzed to find this new discovery of life on that planet. Is this true ?

The report you saw probably referred to a recent paper published by Joseph Miller of the University of Southern California, who has reanalyzed data from the Viking Labeled Release Experiment, one of the life-detection experiments that landed on Mars in 1976 http://www.abc.net.au/science/articles/2012/04/13/3476970.htm. There were four life-detection experiments on... More

Why are the majority of your answers nothing more than repackaged generic no comment answers? Examples of this statement would be when asked about nibiru, the response is Sitchin made it up there is nothing named Niburu,. Tyche, would be the best candidate, being it's size is on par with the size of planet x whcih is said to be as large or larger than jupiter and also a gas planet with something like 30 satellites orbiting it. Here's my question. Science Fiction teaches us that it's rare to find actual rocky stable planets that are capable of supporting complex life, a moon is much more likely candidate than a fully formed planet within the habitable zone. Is it plausible to postulate that life could have formed on one of Tyche's satellites?

The answers I give are based on science, and as my readers will know, I rarely if ever answer "no comment". There is no scientific evidence for NIbiru or Planet X or any other supposed rogue planet. While there are many interesting ideas that have come from science fiction writers,... More

I recently read an article about the increase in size of the glaciers on the himalayan mountains and was wondering what the explanation for this is?

A study was just reported in Nature Geosciences indicating that the largest glaciers in the KARAKORAM mountains of Northern Pakistan have not retreated over the ten years from 1999 to 2008. "The rest of the glaciers in the Himalayas are mostly melting, in that they have negative mass balance, but here we found that glaciers... More

You say Nibiru or Planet X is not real. Please can someone tell me what I am seeing with the naked eye outside my patio each night directly adjacent to the moon. The object when viewed through binoculars looks like a 1980's disco ball eminating static electricity. I want desperately to believe that our planet is safe and there has been nothing to cause alarm, but what I am witnessing with my own eye fits perfectly the description of Nibiru or Planet X.

The only way an object could appear adjacent to the Moon for several nights is if it were in that same orbit as the Moon, and of course nothing is. Please try to remember that the Earth rotates, and that the Moon is also in orbit around the Earth. The... More

I heard on ABC news that in Wisconsin people are hearing moaning coming from the earth and shaking? Are the poles shifting?

No the poles are not shifting. If they shifted by even a tiny amount it would be instantly apparent. None of the astronomical telescopes in the world could point or track, the GPS system would fail, and planes would be crashing all over the world. The very idea of a... More

I have a question about Mars anomalies. All these images can be verified directly from NASA's sources. These two are especially compelling: Giant trees http://www.marsanomalyresearch.com/evidence-reports/2001/020/giant-plants-lakes.htm and Glass Tubes http://www.marsanomalyresearch.com/evidence-reports/2000/001/real-smoking-gun.htm.

These two sets of images are indeed striking, and both have been discussed frequently on the Internet. The features are very large, on a scale of kilometers in size. The “glass tubes” or “giant worms” are simply a trick of lighting and perspective, in which many people see craters as... More