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    Does a finite universe require 4 spatial dimensions?

    A 2-dimensional creature living on the surface of a 3-dimensional sphere could conclude he lives in a finite, unbounded universe. Is it necessary for a 3-dimensional creature to assume there is a 4th spatial dimension in order to conclude the universe is finite and unbounded? I have seen a...
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    Likelihood of confirming past life on Mars

    If there was microbial life on Mars in the distant past, would there be any way to conclusively confirm it? Or would any such attempt be reduced to speculation, like the Martian meteor which "possibly" contained evidence?
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    Universe Splitter

    I stumbled across this app for iPhone which may appeal to those favoring the many-worlds interpretation of QM: I thought it was cool that an app can actually run a quantum experiment each time you use it. I saw mention of it on a Sean Carroll...
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    Another flashlight from spaceship question

    When a spaceship is moving at 150,000 km/sec and you shine a flashlight forward, both an outside observer and the observer on the ship perceive the beam as traveling at c. I think I understand the reason for that when the light is shined forward, but I am confused in the case where he shines it...
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    Could anything artificial survive from the Mesozoic era?

    I am considering a plot for a screenplay in which it would be necessary for evidence of an alien visitation in the Mesozoic era to be discoverable today. Perhaps a message, or tools, or even better, alien technology. I have read that if mankind disappeared tomorrow, all traces of civilization...
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    Guess the high card

    Two decks of playing cards are combined to make a 104 card deck. On the face of each card is written a number. The numbers are all different and can be of any magnitude. You do not know the range of the numbers. The deck is shuffled and placed on the table face down. Your task is to turn over...
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    Proximity of early galaxies to each other

    Given that the universe is expanding and galaxies in general are accelerating away from each other, I would assume that galaxies appearing in the Hubble deep field at a distance of 12 or 13B light years from us should be much closer to each other than is typical for galaxies today. Is this a...
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    Neckline Slimmer They must be selling, judging from the number of commercials I have seen.
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    How do gravitons work?

    I can picture gravity as the warping of spacetime as postulated by GR but I have not heard a descriptive explanation of how a graviton might cause an attraction between two masses, or even if it is a cause in quantum theory. So okay, you have a closed string or a massless particle with a spin of...
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    Black holes responsible for missing ET?

    Scientists are hoping to create tiny black holes here on earth, which they are pretty sure will evaporate almost immediately due to Hawking radiation. While they consider the risk to be almost nonexistent, I can envision some scientist saying "cool -- wonder if we can make a little bigger one"...
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    Stargazing Telescopes: what can you see without CCD?

    My question concerns what deep field objects you can see by eye using a quality 8" or 10" Cassegrainian scope? I understand that you can get some nice photographs with long exposures, but what about just looking through the scope? Planets are a given, but what about spiral galaxies, as an...
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    Spacetime - it warps, it curves, but can't expand?

    Spacetime -- it warps, it curves, but can't expand?? I have a problem understanding this. The general consensus of respected posters in cosmology is that space (and I assume spacetime) is nothing, therefore it cannot expand. Distances just increase. On the other hand, when it comes to gravity...
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    Vacuum energy vs dark energy

    Are these possibly one and the same, or are they completely different concepts? It seems like both are credited for the expansion of the universe, depending on who is doing the talking. dilletante