<p>What makes you think the <a href="http://www.abc.net.au/science/articles/2012/11/28/3642932.htm" rel="nofollow noreferrer">length of a day on Earth</a> has been constant since the formation of the Earth?</p>

<blockquote>
  <p>The length of an Earth day has been increasing slowly throughout most of the Earth's 4.5-billion-year history, says Dr Rosemary Mardling, mathematical scientist at Monash University, and it all has to do with the Moon.</p>
  
  <p>"The reason is that the Moon is attempting to slow down the spin of
  the Earth. The Earth was spinning very much faster when the Moon was
  formed," says Mardling.</p>
  
  <p>Back when the Moon was formed the length of an Earth day was a very
  brief two to three hours, and a much closer Moon was orbiting the
  Earth every five hours.</p>
  
  <p>... the Earth slows down a little bit and the Moon moves away from the
  Earth," says Mardling.</p>
  
  <p>"... The spin down rate is very slow," says Mardling, "It's about two
  milliseconds per century. So the Earth's day is getting longer by a
  500th of a second every century"</p>
  
  <p>... Since the dinosaurs lived during the Mesozoic era, from 250
  million years ago to 65 million years ago, day length would have been
  longer than 21 hours and probably closer to 23 hours.</p>
</blockquote>

<p>Given that the length of a day on Earth has never been constant throughout its history it would be totally impossible to assign a year, month day or time of day for the commencement of the heavy bombardment period or any other event in ancient geologic history.</p>

CC BY-SA 3.0
2017-06-08T09:07:14.413Z
2017-06-08T09:07:14.413Z
Fred
<p>In assigning serial definitions to the stratification of lunar regolith with precise ETA of first impact; what year, month, day and time did the heavy bombardment period begin?</p>

CC BY-SA 3.0
2017-06-08T05:23:24.943Z
is this a joke?.https://en.wikipedia.org/wiki/Late_Heavy_Bombardment
trond hansen
CC BY-SA 3.0
2017-06-08T06:53:29.573Z
Just.. no. Even if dating methods had time-of-day precision over 4 billion years, we would not be able to pinpoint a 'first' crater.
Andrew Jon Dodds
CC BY-SA 3.0
2017-06-09T20:21:22.497Z
Thanks. Another perspective on the issue; is there a HBP algorithm?
user8320
<moon>
What 'time of day' did the heavy bombardment period begin?
user8320
# What 'time of day' did the heavy bombardment period begin?

(Asked by: username_0 on 2017-06-08)

In assigning serial definitions to the stratification of lunar regolith with precise ETA of first impact; what year, month, day and time did the heavy bombardment period begin?

**Tags:** moon

> **Comments:**
> **username_1**: is this a joke?.https://en.wikipedia.org/wiki/Late_Heavy_Bombardment  
> **username_2**: Just.. no. Even if dating methods had time-of-day precision over 4 billion years, we would not be able to pinpoint a 'first' crater.  
> **username_0**: Thanks. Another perspective on the issue; is there a HBP algorithm?  

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## 1 answers

### Answer by username_3 on 2017-06-08. Score: 2

What makes you think the [length of a day on Earth](http://www.abc.net.au/science/articles/2012/11/28/3642932.htm) has been constant since the formation of the Earth?

> The length of an Earth day has been increasing slowly throughout most of the Earth's 4.5-billion-year history, says Dr Rosemary Mardling, mathematical scientist at Monash University, and it all has to do with the Moon.
>
> "The reason is that the Moon is attempting to slow down the spin of
> the Earth. The Earth was spinning very much faster when the Moon was
> formed," says Mardling.
>
> Back when the Moon was formed the length of an Earth day was a very
> brief two to three hours, and a much closer Moon was orbiting the
> Earth every five hours.
>
> ... the Earth slows down a little bit and the Moon moves away from the
> Earth," says Mardling.
>
> "... The spin down rate is very slow," says Mardling, "It's about two
> milliseconds per century. So the Earth's day is getting longer by a
> 500th of a second every century"
>
> ... Since the dinosaurs lived during the Mesozoic era, from 250
> million years ago to 65 million years ago, day length would have been
> longer than 21 hours and probably closer to 23 hours.

Given that the length of a day on Earth has never been constant throughout its history it would be totally impossible to assign a year, month day or time of day for the commencement of the heavy bombardment period or any other event in ancient geologic history.


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