Of Particular Significance

The Venus Transit Brings Up Parallax

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 06/04/2012

A reminder that the transit of Venus across the Sun will be visible a little over 24 hours from now (starting before sunset June 5th in the United States.)  It’s the last of your lifetime, so make your plans now.  Weather forecast across much of the eastern U.S. is pretty bad, I’m afraid. Of course there will be many places to watch on-line.  For more information, I highly recommend http://transitofvenus.nl/wp/ .  Also, though you and I can’t see Venus right now (too close to the Sun), the SOHO satellite can: click here for the latest photo, updated frequently, which shows the sun (at center, blocked out) and the sun’s corona around it, and a white dot approaching the sun, which is Venus (ignore the white horizontal lines, which are an imagining artifact).

The transit of Venus was used, historically, to figure out how big is the solar system (the sun and the planets).  As I’ll explain tomorrow, it wasn’t that hard to figure out how large are the distances between the sun and the planets relative to one another, but getting the overall scale — the absolute distances — was a much harder problem.  The first measurement accurate to a couple of percent came from the transits of Venus in the 1760s.  I’ll explain (roughly) how this works tomorrow; the technique relies on the principle of parallax, a principle which lies behind our own ability to perceive depth, and is used by astronomers to measure distances to (relatively nearby) stars.

[Reminder: two events coming up in which I’ll be speaking:

First, a panel discussion June 7th, sponsored by SoNYC (Science online New York City), entitled “Reaching out of the Ivory Tower”, about the experiences of scientists who are reaching out to the public. (free tickets required, click here for details and tickets.)  Panelists: Ethan Perlstein, Sarah Weisberg, Matt Strassler, Jeanne Garbarino.  Location and time: Weiss 305, Rockefeller University, East 66th and York Ave. New York, NY, Thursday, June 7,2012 from 7:00 PM to 9:00 PM (ET)

Second, again in New York, Saturday June 16th at 2pm, I’ll be giving a lecture (click here for details):  THE EINSTEIN OBSESSION: SCIENCE, MYTH AND PUBLIC PERCEPTION.]

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5 Responses

  1. I’m sure Matt will reply, but I think he has some good articles on his site related to this. Check out this one here:


    I believe some of your confusion stems from your definition of “space.” The universe is expanding because space is expanding. They are one and the same. The current view based on the available data is that the universe will continue expanding forever.

  2. Dear Sir
    I have a question that kept coming into my mind , and i thought it might be philosophical- sort of- and that kept me from asking any scientist of theoritical physics .
    but decided you may have an opinion that opens new window for me.
    the question is
    the universe is expanding thats ok but , into what ? i mean where its expanding ? in other words what is that space our universe expands in? if any exists ? i hope iam not dsiturbing you , and sorry if iam .
    thank you in advance .

  3. imagine if gravity,was simply the flow of time…the unified theory writes itself from here…i can do that,,but the specialised physics,and collaborating science and mathematics,is best in the hands of experts…
    thank you for reading,and i hope it was of interest

  4. hi Proff Strassler,,,thank you for the recent post,,,unfortunately a very cloudy couple of days in melbourne,,so i appreciate the pics,but what i enjoyed the most was your post about parallax,,,its funny how sometimes the simplicity of a theory,is all the evidence a theory requires,,the depth of its fundamental simplicity,is of great significance,because that allows it to be common to all,,,the more generality of a theory the more its unified as the common…its either space or time,,,if its both at once its neither,if its either/or its none,,,the first observed,is unmeasured,and the first measured is second observed….i had intended to keep it light,but yet again,got distracted by a common singularity….
    anyway thanks again for the post,parallax will be one of so far a trilogy of the simplest,most fundamental laws,that imply the singularity of time as the unified common…its simplicity is what undermines its face value,but the law of absolute singularity,is the fundamental generality of totality…

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