[ExI] Milky Way escape velocity
spike66 at att.net
Tue May 1 14:20:33 UTC 2012
From: spike [mailto:spike66 at att.net]
Sent: Tuesday, May 01, 2012 7:18 AM
To: 'ExI chat list'
Subject: RE: [ExI] Milky Way escape velocity
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Stefano Vaj
Sent: Tuesday, May 01, 2012 4:48 AM
To: ExI chat list
Subject: Re: [ExI] Milky Way escape velocity
On 30 April 2012 22:49, BillK <pharos at gmail.com> wrote:
We recently mentioned the velocity required to escape the Milky Way
galaxy - over 1 million miles per hour.
Million? miles?! hour? I could do the math, but while it sounds much, I do
not have from the top of my head the vaguest idea of the fraction of c we
are discussing here... :-)
BOTECs in round numbers that I can recall, the distance from the sun to the
center of the Milky Way is about 27,000 years, and the orbit period is about
250 million years, so the orbit speed is about 0.1 milli-c, and escape
velocity from any round orbit is square root 2 times the tangential velocity
so escape velocity from here would be about 140 micro-c, and a micro-c is
about .3 km/sec so escape is about 40 km/sec.
I don't know where I went wrong, but this calc feels like it is off an order
of magnitude to the low side. I think escape velocity from here is more
like 400 km/sec. What did I do wrong?
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