limacharley

limacharley t1_j6vb0y3 wrote

The key is how dark your skies are. This is not a bright comet (Magnitude 5 last time I looked). That means it is just barely visible as a dim smudge with the naked eye in dark skies. It may not be visible if you are in an area with light pollution. The brightness does not change very much from day to day, so, if your skies are dark, then it shouldn't be noticeably harder to see it tomorrow than it would be today.

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limacharley t1_j18i335 wrote

Galaxies are usually part of a Galaxy Cluster, which is held together by gravitation. The expansion of the universe is not fast enough to overcome gravitational forces, so galaxies within clusters should not be any further apart now than they were billions of years ago. Even galaxy clusters are gravitationally bound into Super Clusters. There must be a large enough scale where yes, things are spread out more than they used to be, but I have not heard of any observational evidence of that (granted I have not worked in the field for more than 10 years now).

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limacharley t1_j01udkn wrote

There would be huge compression at the point of impact, which would cause fusion of very heavy elements and maybe formation of a neutron star. In a supernova, the compression from the collapsing star leads to a reverse shock which blows apart the outer layers of the star. That might happen in your scenario as well. In any case, you are going to end up with zero stars and lots of debris.

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limacharley t1_iztlduv wrote

You are correct that SOMEONE has to be early. The problem is that there is no logical reason why the first intelligent life should just be arising now. Everything we know about the uni verse suggests that earthlike conditions should have been possible since the rise of the Population I stars (modern stars which seeded the galaxy with most of the elements heavier than helium). That was many billions of years ago. It only took humans a couple million years to go from upright apes to escaping our planter's gravity well. There is no known physical barrier to us colonizing the solar system and then the galaxy within a couple million years at most (assuming the light barrier can never be crossed). So, if intelligent life has been possible for billions of years and it should only take millions to fill up the galaxy, then where is everybody? That is the problem with saying we are at the beginning of the distribution. Everything we know says the distribution should have started long ago.

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limacharley t1_irq04yh wrote

Some animals sense magnetic fields. Others follow the stars. Of course, it is pretty easy to tell what direction you are headed just by noting where the sun is. In the morning your shadow points west. In the evening your shadow points east. At noon your shadow points north (in the northern hemisphere)

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