Wikipedia:Reference desk/Archives/Science/2022 November 11

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November 11

Rose smell

I understand some roses do not have a sweet smell like they used to. Why? I thought all roses had a sweet smell.--Christie the puppy lover (talk) 19:01, 11 November 2022 (UTC)

• This is not exactly new, but breeders have often sacrificed odor for other traits, particularly shelf life, when breeding commercial roses. Also, there are rose species, such as Rosa agrestis (field briar) that have hardly any odor. Abductive (reasoning) 19:12, 11 November 2022 (UTC)

"Historically all roses had an odour, but after the introduction of almost scentless China Rose and the larger Tea Rose, both from China in the 19th-century smell was slowly bred out from some roses". [1] Alansplodge (talk) 19:15, 11 November 2022 (UTC)

There are many true rose species and many cultivars grown as garden roses or to be used as cut flowers. Many of these varieties are bred primarily for their looks, often by drastic inbreeding, while not selecting for smell – and natural selection is sidelined. So it is no wonder that some cultivars lost the captivating smell of their wild ancestors. Tomatoes are now largely selected for good looks (a smooth shiny skin) and long shelf life; the effect is that they have become much less tasty.  --Lambiam 19:28, 11 November 2022 (UTC)

Right, and expanding on that a bit; odor and flavor are meant to attract pollinators and animals to eat the fruit and spread the seeds, and so natural selection tends to favor a period of the most intense odor and flavor to coincide with peak fertility and ripeness. If you breed just for longer periods of freshness, you necessarily have to spread the same amount of aromatic chemicals over a longer time period. Abductive (reasoning) 19:59, 11 November 2022 (UTC)

• Thanks all - great answers. Now I get it.--Christie the puppy lover (talk) 21:04, 11 November 2022 (UTC)

• But do you?

Vitae Summa Brevis Spem Nos Vetat Incohare Longam

They are not long, the weeping and the laughter,
    Love and desire and hate:
I think they have no portion in us after
    We pass the gate.

They are not long, the days of wine and roses:
    Out of a misty dream
Our path emerges for a while, then closes
    Within a dream.
                   Ernest Dowson

MinorProphet (talk) 22:39, 15 November 2022 (UTC)

Foo in observable universe

At what rate, if any, estimates like the number of foo in observable universe become obsolete due to universe's expansion? I understand that large numbers like 200 sextillions of estimated stars likely wouldn't considerably change over years, but does universe expand fast enough to make such estimates, including Eddington number after 82 years, dated (warranting placing, say, year or century of estimate)? 212.180.235.46 (talk) 21:33, 11 November 2022 (UTC)

On cosmological timescales, 82 years is completely insignificant, so a 1930s estimate of the number of protons in the observable universe would still be a reasonable estimate today.

Over much longer time periods, the observable universe will indeed change due to expansion of the universe. First, over the next few billion years, light from some more distant objects than have been observed will reach us, having not yet had enough time to do so, causing an increase in the size of the observable universe and thus raising the Eddington number. However, because the expansion of the universe is accelerating, everything not gravitationally bound to the Local Group will eventually recede beyond the cosmological horizon, on the order of 10¹¹ to 10¹² years from now (when the universe reaches 100 times its current age). In this case, one could say the mass of the observable universe is approximately the mass of Milkomeda, which is far less than the mass of the observable universe today. Of course, these estimates assume several conservation laws are upheld – mainly mass–energy; it is possible that particles are "lost" by collisions and conversion to energy, but the total mass–energy is unchanged – and does not consider the possibility of proton decay, both of which might alter the number of protons in the universe on even longer timescales (around 10³⁴ years for proton decay if it occurs).

In any case, humanity won't be around long enough for a perceptible change in these estimates to occur. ^Complex/_Rational 05:05, 12 November 2022 (UTC)

While (in our best scientific understanding) such physical values themselves are constant or change only extremely slowly, slower than anything we might detect by direct measurement, our estimates for such values may change rapidly. In 1929, when Edwin Hubble published his redshift observations, including his estimate of what is now known as the Hubble constant, the age of the universe, based on the estimated value of this parameter, was thought to be about 1.8  billion years. By 1952, revised estimates of the Hubble constant had increased the estimated age of the universe to about 3.6 billion years.^[2] The currently accepted best estimate (as of 2018) is about 13.8 billion years. One might be tempted to define a meta-Hubble constant for the speed of growth of the estimated age (observed to have been about 135 million years per year).  --Lambiam 08:53, 12 November 2022 (UTC)