• The forum software that supports hummy.tv has been upgraded to XenForo 2.3!

    Please bear with us as we continue to tweak things, and feel free to post any questions, issues or suggestions in the upgrade thread.

Interesting Items...

It can take a photon 40,000 years to travel from the core of the sun to its surface, but only 8 minutes to travel the rest of the way to Earth.

Are photons labelled, then?
 
It can take a photon 40,000 years to travel from the core of the sun to its surface, but only 8 minutes to travel the rest of the way to Earth.

Are photons labelled, then?
:o_O:Hmm. If a photon is delayed by random action in the sun, including absorbtion and subsequent re-emitting, how on earth sun can you keep track of an individual photon? The photon that emerges from the surface is unlikely to be the same one that was created at the start of the process.:confused:
 
It can take a photon 40,000 years to travel from the core of the sun to its surface, but only 8 minutes to travel the rest of the way to Earth.

Are photons labelled, then?

:o_O:Hmm. If a photon is delayed by random action in the sun, including absorbtion and subsequent re-emitting, how on earth sun can you keep track of an individual photon? The photon that emerges from the surface is unlikely to be the same one that was created at the start of the process.:confused:

I hate to burst you guys' bubble of fake news, but I suspect this is a theoretical thing. At least until Trump's America puts a couple of scientists into the middle the sun to prove it.
 
So it seems a remarkable coincidence that there is a "Friday 13th" superstition when the 13th is most likely to fall on a Friday. It leads me to wonder whether there is a connection.
I just realised (while writing about the Gregorian and Julian calendars - see https://hummy.tv/forum/threads/assume-v-presume.1453/page-142#post-106474), that it is the Gregorian calendar that provides the coincidence, and the Friday 13th superstition probably pre-dates the introduction of the Gregorian Calendar (1582 in Rome, 1752 in Britain), therefore cannot be connected.
 
Astronomy has dealt with this problem by coming up with the concept of the Julian Day Number. This is a time scale where the primary unit is a day, counted from a datum sufficiently far back as to have positive values for all astronomical events of any historical interest at all. This removes any inconvenience or confusion with the missing year 0, different calendar systems (eg Julian/Gregorian, Chinese, etc etc), or the 11 days that got removed from the calendar in 1752 when the Gregorian* system was adopted in Britain. With no months (with varying numbers of days) or years (with varying numbers of days) to deal with, JD is a linear scale convenient for time calculation - it just needs a bit of conversion when presenting a JD as a calendar date (in whatever calendar you choose).
This leads to more questions I don't know the answer to. "Primary unit is a day" - what sort of day? The "day" of common experience is the period of time between the passage of the Sun in the sky, and that varies a little day by day due to the eccentricity of the Earth's orbit so we have to talk about an average day (averaged over a year), but even then the length of a day (measured exactly) drifts. If you are doing a calculation in celestial mechanics (eg the orbit of a long-period comet), the time reference is going to be the definition of the second - but converting that to rotations of the Earth may result in an error due to the inaccuracy of the rotation period over a long period of time.

:confused:

But I guess it doesn't really matter. If one Julian Day is 24 hours as measured using the international standard second, conversion from JD to calendar date will yield the correct result for any time in recorded history. It might drift into the wrong date outside that, but as long as the JD scale remains linear (and you don't keep converting to calendar dates and back again), it's irrelevant.
 
A rose to store energy

28 February 2017
Monica Westman Svenselius


rose-supercapacitor-thor-balkhed_liu.jpg

A special structure for storing energy known as a supercapacitor has been constructed in a plant for the first time. The plant, a rose, can be charged and discharged hundreds of times. This breakthrough is the result of research at the Laboratory of Organic Electronics at Linköping University.
In November 2015, the research group presented results showing that they had caused roses to absorb a conducting polymer solution. Conducting hydrogel formed in the rose’s stem in the form of wires. With an electrode at each end and a gate in the middle, a fully functional transistor was created. The results were presented in Science Advances and have aroused considerable interest all over the world.

New material

One member of the group, Assistant Professor Roger Gabrielsson, has now developed a material specially designed for this application. The material polymerizes inside the rose without any external trigger. The innate fluid that flows inside the rose contributes to create long, conducting threads, not only in the stem but also throughout the plant, out into the leaves and petals.

“We have been able to charge the rose repeatedly, for hundreds of times without any loss on the performance of the device. The levels of energy storage we have achieved are of the same order of magnitude as those in supercapacitors. The plant can, without any form of optimization of the system, potentially power our ion pump, for example, and various types of sensors,” says Eleni Stavrinidou, Assistant Professor at the Laboratory of Organic Electronics.

The results are now to be published in the prestigious scientific journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Excellent performance

“This research is in a very early stage, and what the future will bring is an open question,” says Eleni Stavrinidou.

Some examples are autonomous energy systems, the possibility of harvesting energy from plants to power sensors and various types of switches, and the possibility of creating fuel cells inside plants.

“A few years ago, we demonstrated that it is possible to create electronic plants, ‘power plants’, but we have now shown that the research has practical applications. We have not only shown that energy storage is possible, but also that we can deliver systems with excellent performance,” says Professor Magnus Berggren, head of the Laboratory of Organic Electronics, Linköping University, Campus Norrköping.

The research into electronic plants has been funded by unrestricted research grants from the Knut and Alice Wallenberg Foundation. The foundation appointed Professor Magnus Berggren a Wallenberg Scholar in 2012.
 
Last edited by a moderator:
Just what we want radioactive batteries. Dirty bomb anyone?
Who didn't know about get_iplayer? Just don't tell the BBC.
 
Back
Top