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Record number: WCP2876

Sent by:
Edmund Taylor Whittaker
Sent to:
? Benett
22 July 1907

Sent by Edmund Taylor Whittaker, Dunsink Observatory, Co. Dublin, Ireland to ? Benett [none given] on 22 July 1907.

Record created:
30 November 2011 by Mayer, Anna


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LETTER (WCP2876.2766)

A typical letter handwritten by author in English and signed by author.

Held by:
British Library, The
Finding number:
BL Add. 46437 ff. 217-218
Copyright owner:
Copyright of the Edmund Taylor Whittaker Literary Estate.

Physical description

Transcription information



[[1]] 1 2 3

Dunsink Observatory,


July 22nd, 1907

Telephone -- Castleknock, No. 14.

Telegrams -- Blanchardstown

My dear Benett

At last our guests have left us & I can settle down to work: I am exceedingly sorry for the delay in discussing Dr Wallace's suggestions.

An extreme degree of uncertainty is attached to all estimates of planetary temperature. One realises this e.g. when one walks from the outer air into a greenhouse on a perfectly calm day in summer, when there is no artificial heat applied: the greenhouse & the outer air receive exactly the same amount of solar radiation, & yet are at quite different temperatures - owing [[2]] of course largely to the circumstance that glass is comparatively transparent for the incident solar radiation & comparatively opaque to the radiation of longer wave-length emitted by the heated walls & plants inside -- so that it acts as a radiation--trap. If there is anything on Mars which can act in this way, the temperature of Mars might be almost anything short of the Sun's own temperature!

The amount of radiant energy received from the Sun in one second is proportional to the inverse square of the distance [1 word illeg.] from the Sun. This energy received must exactly balance the energy radiated away, in order [[3]]4 to keep the temperature steady. But the energy radiated away is by Stefan's law proportional to T4, where T is the absolute temperature of the planet. So T4 must be proportional to 1/r2, & therefore T must be proportional to 1/√r. This would give -44°C. for as the temperature on Mars.

Dr Wallace in his calculation appears to assume that T is proportional to the radiant energy received: but I can't follow the reasoning grounds on which this assumption is based.

However, I make no secret of my own belief that we know nothing whatever about the temperature of Mars.

It is very kind of you & Miss Bennett to think of inviting Mr T.W. Russell5. We [[4]]6 should much like to meet him, as I think he knows various relatives of mine who are engaged in Temperance & Political work. Any day would suit us.

The balloon ascent this morning was a failure, owing to the cloudy & foggy weather. Better luck next time.

Ever your sincerely | Edmund T Whittaker7 [signature]


1. Top centre, unknown hand, "Edmund T Whittaker".

2. Top right, unknown hand, "217".

3. Top left, Trinity College, Dublin stamp.

4. Top right, unknown hand, "218".

5. Sir Thomas Wallace Russell, 1st Baronet PC (1841 – 1920). Irish politician and agrarian agitator.

6. Bottom right, British Museum stamp.

7. Edmund Taylor Whittaker F.R.S., F.R.S.E. (1873 – 1956). English mathematician.

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