# My talk on the age of the Earth

Thanks to Rob Grigjanis, I got the link to the talk I gave on Saturday on the wildly varying age of the Earth. The full day’s talks are below and mine begins soon after the 5:25:00 mark.

If you do not know how to skip to the part where my talk begins, you can go here where it has already been cued up for you.

Rob and I had a discussion about my discussion of Kelvin’s role in the comments section of my earlier post announcing the talk that those interested can go and read.

1. Marshall says

Just add “&t=#h#m#s” (any subset of h, m, s), or right-click the video and select “Copy video URL at current time.”

2. enkidu says

Hi Mano.
I’ve just finished watching your presentation on Youtube, and I thought it was a very clear and succinct summary of the topic. I have also read you book and I liked your comments on the question of “if the age of the universe could change again”, that the integration of many fields of science virtually lock in place the current age.
I have a thought (though I am definitely not a Physicist) that you might like to expand on in a post. As you say, the critical mass of the universe determines if it will eventually collapse or expand indefinitely. Since the Universe appears to be flat, in terms of mass, what would that imply for the ultimate fate of the Universe? Would it end up in a steady state, for example?

3. Mano Singham says

enkidu @#2,

If the density of the universe is indeed equal to the critical density, it will keep expanding but slow down until it approaches a state of non-expansion asymptotically, though it will never reach it.

An analogy is that of throwing a ball straight up. It will slow down as it goes up. If its initial velocity is less than the escape velocity, then at some point it will stop and return to Earth. If its initial velocity is greater than the escape velocity, then the ball will head out into space forever and its velocity will never become zero.

What will happen if the ball has exactly the escape velocity? It will keep going up but get slower as it goes, its velocity approaching zero as the distance approaches infinity, which of course it will never actually reach.

4. lochaber says

Thanks for posting this, I was rather busy this weekend, and was unable to make the initial zoom meeting, but was interested in the presentation.

As much as people like to laugh about the previous incorrect attempts to date the age of the Earth, I think it’s interesting just in that they were looking for a way to solve a difficult question, and the various methods they used in an attempt to answer that question.