Ubitag said:
A hundred years ago was a long time. 300 yrs ago there was no USA.
Yet u expect us to believe the earth is over a billion yrs old?
The sun just burns forever, makes its on energy source.
OK I'll bite.
It can be really hard to grasp the age and size of the universe. If you took the 4.5 billion age of the Earth and put it onto one calendar. Life appeared at 2/25. Humans started walking on 12/31 at 11:30 am. The Industrial Revolution started at 11:59 pm.
The history of estimating the age of the Earth is pretty interesting. Estimates have been all over the place, but they really got modern and scientific in the 1860s. Kelvin put it at 400 million by estimating temperatures. Biologists estimated it to be much longer to have enough time for evolution to occur. In 1897 John Joly estimated 100 million by measuring ocean salt content. Radioactivity hadn't been discovered yet, so none of those estimates included radioactive decay. All that changed with the invention of Radiometric Dating in the 1910s. This technique compares the amount of a radioactive isotope to the amount of its decay. There is an assumption here that has been backed up and thoroughly tested that the rate of decay is constant.
The Sun doesn't burn forever or make it's own energy. The Sun is about half way through its lifecycle. It's been burning for 4.5 billion years, and has about 5 billion left. Comparatively our Sun is average. Betelgeuse, the brightest star in the Orion constellation on the left shoulder is 700 times the size of our sun. Interestingly, Betelgeuse has been dimming recently which could mean it might go supernova and become half as bright as the moon.
The sun burns by fusion. Two atoms combine together to form a new atom that is smaller than the combined mass of the two previous atoms. This lost mass is changed into energy. You probably know the equation that calculates that: E=mc2.
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Each of us has our own distinctive DNA and even our finger prints are different. Billions of people have come and gone yet all different....my goodness, what are the odds.
This is hard to answer because we still don't know exactly how much of our DNA is useful yet, and we don't know for sure which DNA combinations would create a non viable human. We have 25,000 genes. Each gene can have 4 bases G, A, T, C. The number of basepairs in the human genome is 6,469,660. Take .5% of that (an assumption on how much would produce a viable human) and factor it you get 4.3744x10^131838. If we estimate that 108 billion humans have existed, then the odds of a repeat are one in 2.469 x 10^131831.
This was hard to find numbers on because the knowledge has been changing a lot on it in the past few years. I found all kinds of different answers. So take my few minutes of research with a grain of salt and just think that the odds are really huge.
Sources:
https://www.reddit.com/r/theydidthemath/comments/7f7wmr/request_how_many_possible_dna_combinations_are/https://biomimicry.net/earths-calendar-year/https://www-istp.gsfc.nasa.gov/istp/outreach/workshop/thompson/facts.htmlhttps://en.wikipedia.org/wiki/Age_of_the_Earthhttps://en.wikipedia.org/wiki/Radiometric_datinghttps://genetics.thetech.org/ask/ask149https://www2.palomar.edu/anthro/biobasis/bio_3.htm