If our universe is 4.6 billion years old as some scientist suggest, than our sun is halfway through it's?

Question

10 billion year life expectancy. As stars get older, they also get brighter. Our sun is supposedly 40% brighter than it was 4.6 billion years ago. If we go back 3.5 billion years to when life supposedly first started, the sun would have been 25% bright than it is now. The sun being less bright, also means less heat was produced. This less heat would have lowered the temperature of the earth from an average 59 degrees to an average below freezing.
Can anyone explain how life would have started with average temperatures below freezing?

Answer 1

SensibleChristian............This question has to do with the inverse-square law, and the temperature changing exponentially.

One thing that abiogenesis needs for life to start is heat. I never heard a scientist give a good explanation for this question.

Mooseback...........what denser atmosphere? That's a new one I never heard about.

Answer 2

Interesting question. First, the difference between when life arose and now is 25%, not 40%. Second, there isn't a direct change in climate based solely on the heat of the sun. Such things as the greenhouse effect alter how much heat is held in. Given the different gasses in the atmosphere the differences are currently unknown.
Furthermore, life need not have arisen at the surface of the earth. There's a lot of people who now believe that life could have arisen around deep ocean thermal vents. If so, surface temperature wouldn't have been a factor.
There's plenty more to say on the subject, you can start with the link below. And then maybe figure out why you ask science questions in religion chat. There are plenty of physicists and such who would be happy to address your arguments in the science section.

Answer 3

There are a few problems with your theory:

The universe is more than 4.6 billion years old. That's the age of the planet Earth and it's sun. The age of the universe, in Big Bang cosmology, refers to the time elapsed between the Big Bang and the present day. Current observations suggest that this is about 13.7 billion years, with an uncertainty of about +/-200 million years.

Long, long ago (some 5 billion years ago) in a perfectly ordinary place in the galaxy, a supernova exploded, pushing a lot of its heavy-element wreckage into a nearby cloud of hydrogen gas and interstellar dust. The mixture grew hot and compressed under its own gravity, and at its center a new star began to form. Around it swirled a disk of the same material, which grew white-hot from the great compressive forces. That new star became our Sun, and the glowing disk gave rise to Earth and its sister planets. We can see just this sort of thing happening elsewhere in the universe.

During the formation of our solar system, the star Sol, was approximately 2/3 as bright as it was today. However, the process of ignition, within the sun, and the collision of planetisemals (smaller planetary bodies which contributed to the overall 'end result' planets), generated heat and energy...which contributed to the conditions allowing life to spring forth on this planet.

The oldest surviving rocks on Earth were formed some 600 million years after Earth first formed. So all of the activity of Earth's birth was already ancient history (except for a possible "late bombardment" of the last stray planetesimals around 4 billion years ago). The oldest rocks, dated by the uranium-lead method as about 3.96 billion years old, show that there were volcanoes, continents, oceans, crustal plates, and life on Earth in those days. While the eons that followed were full of strange stories and far-reaching changes, the Earth had taken on its basic structure long before.

Answer 4

The Universe is estimated to be more than 14 billion years old, not 4.6 billion. The 4.6 billion is the estimated age of earth. The sun may be 50% through its life span as a yellow dwarf-type star, but it has 5 billion years to go and it may go on much longer as a white dwarf. Your comments about earth's temperature are speculation. The earth has been losing heat from its own formation so it would likely have been warmer in its infancy from geologic and formation processes. In addition, there was likely more of a greenhouse gas effect before plant life took hold to convert the atmoshphere. Life processes probably don't need temperatures over freezing. Much life in the ocean exists at temperatures of less than 32 degrees Farenheit -- sea water requires much lower temperatures to freeze due to its chemical makeup. Thermal vents in the ocean support life even in the absence of sunlight and heat, warmth being provided by the thermal vent. There is no reason to think conditions were that different or that such islands of life in severe conditions did not exist previously.

Answer 5

I don't know where you got all your numbers, and I'm not going to take time right now to research them, but off the top of my head I suspect you are wrong not only in the values you cite, but in that you are leaving out other information.

For example, you are completely omitting the greenhouse effect and geothermal heat.
-- edit --
Thinking a bit more, I realized I should have also questioned another claim. You seem to be asserting that the brightness of the sun increases in some smooth, nearly linear fashion. But that's totally wrong. Every start goes through very long phases where there is primarily one kind of fusion happening. First hydrogen fuses to helium, and then later helium fuses into heavier elements. The sun is still fusing hydrogen, and has been for all of its 5 billion years. I bet your claim that the sun was only 25% as bright 3.5 billion years ago is totally wrong. Can you cite a source?

Answer 6

I wouldn't judge the life of the universe by that of our star.

Supernovas have occurred in the universe, and I'm sure they were older.

Who is to say that life on Earth started 4.6 billion years ago, and not 3.6?, in fact, I believe (not 100% sure) that it started in the 3's, at least that's what came up in a conversation earlier with a friend of mine studying ap Biology.

That's the current belief at least.(I think)

So woo hoo, it didn't start at below freezing!

Answer 7

The latest figures for the age of the universe hover around 15 to 18 billion years old.And you presume that the sun began to shine when the universe first came into existence.

Answer 8

Hold up a second, it's the Earth that 4.4-4.6 billion years old according to science, not the universe, the universe is supposed to be 14.4 billion years old. Besides you're only talking about the main-sequence evolution of the sun, not it's complete evolution.

Answer 9

Did you learn your solar history from a comic book?

The sun won't get brighter because it's heating up, it will get brighter because it has used up all of its hydrogen and will then have to use helium which takes more energy to fuse (ergo: brighter sun).

The sun was NOT cooler when life began.

Answer 10

4.6 billion years old? I really don't think we can determine how old the universe really is. Ask science for evidence on how old the sun is for example, and they won't give you a straight answer. Common sense will tell you if you cannot estimate on how old the sun is, you cannot therefore estimate how old the universe is. Sure you'll get some vague answer, but no hard physical proof. And how do you actually examine that?

Answer 11

Yea if thats true uve only got another 5 billion years to live through to see the end.