# The Naked Scientists Forum

### Author Topic: How long does the present last?  (Read 4715 times)

#### thedoc

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##### How long does the present last?
« on: 06/06/2014 06:30:02 »
Robert cattle asked the Naked Scientists:

There is the past, the present and the future.
My question is, how long does the present exist for? Or does it exist?
What do you think?
« Last Edit: 06/06/2014 06:30:02 by _system »

#### Bill S

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##### Re: How long does the present last?
« Reply #1 on: 06/06/2014 12:17:38 »
Conventionally we divide time into past, present and future.  Everything we plan to do is in the future, every thing we have done is in the past, every thing we do, we do in the present.  The problem comes when we try to look closely at “that infinitesimal point of time we call the present”.   The more closely we look, the more elusive that “present” becomes.  We call it infinitesimal, but by that do we mean “infinitely small”, or “so small that we cannot even think about its smallness”.  If we mean the former, then we run into problems regarding the actual existence of something that is really of infinite smallness.  If we are talking about the latter, then we can be absolutely sure that some one will have tackled the problem of thinking about how small the smallest object could be, or how brief the shortest finite time could be. Max Planck did.  He calculated that the shortest period of time that could have any significance was 10^-43 seconds.  If time is quantized this is probably the quantum of time, and must be the duration of the present, but we don’t know if time is continuous or quantized.  If it is quantized, we reduce time to Planck’s time, or to nothing, but beware, nothing is not always what it seems. :)

#### petm1

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##### Re: How long does the present last?
« Reply #2 on: 06/06/2014 22:56:47 »
The way I see my present moment, my one second frame of reference created by my consciousness, is as a receiver and processor the leading edge of which is the focal point within my eyes and the trailing edge is action.  This con-moving field anchored to my own body by my count using the watch on my arm is about one second long.  Or if you want to think short then I would say that emission only happens in the present.

#### allan marsh

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##### Re: How long does the present last?
« Reply #3 on: 07/06/2014 11:17:11 »
Please, I am not being awkward but the electrochemical human brain activity means that there is about 200 ms between the past and Now!
That view is correct But I really refer to a rock without brain.
Does that Rock have a NOW or just a Past and Future??

It all has a reflection as to what is reality, not just for humans, but for flys and finally a lump of Rock

#### Bill S

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##### Re: How long does the present last?
« Reply #4 on: 07/06/2014 13:41:58 »
Quote
That view is correct But I really refer to a rock without brain.

Allen, I a bit unclear as to what you are asking here.  Are you wondering if a rock experiences time?

#### allan marsh

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##### Re: How long does the present last?
« Reply #5 on: 07/06/2014 20:21:45 »
I should come a little clearer because I used the inanimate object ie a rock but the real entity i refer to is the PHOTON
That won't help if your view is simply thru human eyes
The reason I ask is to see if anyone answers a technical question i have about superposition and entanglement

Perhaps you should use one of Richard Feynman,s  premier quotes!

#### jeffreyH

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##### Re: How long does the present last?
« Reply #6 on: 09/06/2014 00:05:53 »
We can't determine the Planck time accurately without determining G the gravitational constant which depends upon the Planck units. In the case of the photon we need the Planck time and Planck length to relate c the speed of light to quantum mechanics. Although I believe it is not absolutely necessary to nail down either G or the Planck units others will disagree. The work I am undertaking will make the calculation of G unnecessary and may lead to an accurate value for Planck units.

#### The Naked Scientists Forum

##### Re: How long does the present last?
« Reply #6 on: 09/06/2014 00:05:53 »