I'm crying, and I can't stop.

I've been crying for three days, now, ever since they brought me up here to the mother ship. I've tried to stop - it isn't manly, and it isn't dignified - but I can't. They are kind - bring me meals, and a sedative so I can sleep nights. Might as well call it night, though here in orbit it doesn't seem to matter much, just eight hours in twenty-four.

Eight hours that I go quiet, and forget about it all, and don't dream, thank goodness. It must be getting on their nerves, all this crying, but they're so polite. They never mention it.

I know what will happen if I can't stop, though.

When SETI informed us that there were, indeed, 'aliens' from other worlds - that they'd received Communications from Out There - I was as excited as everyone, I suppose. Particularly as I realised I stood a good chance of being among the welcoming party when they finally got here.

They'd apparently intercepted Voyager, and been as excited as we would have been. Only, they had warp speed capabilities, and could come visit. They sent us a calling card - proof that they knew pi, and had language, and music...

Oh, that music. We were surprised, having sent Beethoven and Chuck Berry. They sent a single-voice recording - no instruments - that, well, made the hair on the back of your neck stand up. In a good way, of course. It's just that every person who heard it had exactly the same feeling - as if the tune were so obvious, somehow, as if you couldn't believe you'd never heard it before (though you hadn't), but having heard it, you couldn't imagine the world without it.

The only thing they didn't send was a picture of themselves, the way we had. And that gave us pause for thought.

When the people on our end of the phone realised the Xenans, as they called themselves (they managed to send messages to us in our major languages, being better at that, too, it seemed, than we were), were headed our way and would arrive within months, we on the reception committee started preparing. We mapped out sightseeing tours, arranged for security, the whole nine yards. We even knew what we wanted to say: Welcome, hope you come in peace for all Beingkind, that sort of thing.

What worried us most, however - and what took up most of our practice time - was controlling our reaction to the way the aliens were likely to look. After all, the last thing we wanted to do was to spoil the first impression we'd make on these lovely people - who had travelled lightyears to see us, after all, and who had sent some very nice presents ahead of them, including the solution to the Riemann Hypothesis - by recoiling in horror from their slimy tentacles, or compound eyes, or hairy, apelike bodies.

So we practised. Hiring actors in prosthetic makeup, we practised making our speeches without blinking in front of science fiction's most imaginative monsters. This was sometimes hard just because they made us laugh. Less easy were the mock state dinners. Keeping one's rubber chicken down while one's neighbour dug into a bowl of juicy grubs covered in tomato sauce was a job for the stout of heart. We remembered it was for humanity, and we persevered until we could smile and inquire politely if the motor oil was a good year.

Sociologists, psychologists, philosophers, even theologians lectured us about the possible differences in outlook between ourselves and our guests. Linguists warned us about pronouns, ethologists about body language. After months of preparation, we felt ourselves ready.

How wrong we were.

The young (?) Xenan female - I know she is female, from her short hair, and her dress, and the timbre of her voice - who has just brought me a delicious aloo palak seemed encouraged to see me writing.

'Why, how wonderful, Dr Bhabha.' She stretched out her hand, as if to touch my shoulder, but when I involuntarily shrank back withdrew it. 'I hope you enjoy your meal.'

I can eat and cry, I have found. But the food is delicious. It is always delicious - each meal the best I have ever tasted.

The shock of their arrival - their technological superiority, their knowledge of us, their appearance - was compounded by the horrendous news they brought. There was no question about it - Earth had only a short time to live. Events which even they could not prevent would lead to our sun's going supernova before its time. We had only two decades to prepare the mass evacuation.

The Xenans have been gracious, helpful, and utterly kind. (They are unfailingly kind.) They have made their vast resources available to us. They have promised us homes on their inhabited worlds. Such worlds are few and far between, it seems. This is not a gift to be weighed lightly. It is the gift of survival for the race of humanity.

Why can't I stop crying? My own survival depends upon it. If I learn to stop, I might save others. The others who can't stop crying, and who, if they can't, will not be able to make the journey.

For at the end of the journey are Xenans.

When the first delegation - four males, two females - stepped to the designated meeting platform, symbolically chosen at Cape Canaveral, the spot from which the first humans had left to go to the moon, we understood our mistake - and the revelation was devastating. For me, for so many of us.

The world was watching, of course. I believe that the satellite television audience was the highest for any event in history. After a few words of greeting, the leader stepped back, and a male and a female stepped forward, and, with the most gracious of smiles, began to disrobe, apparently both to satisfy our natural curiosity and to allay our fears about weapons. To show trust.

How misplaced was that trust, I wonder? What we saw destroyed our hearts.

Two Xenans, the male and female distinguished mainly by slight differences in their musculature, by different dress and hair style. Bipedal, bilateral symmetry, binocular vision, hair on their heads, none on their bodies.

But - they glowed. And they were beautiful. Every inch of their skin glistened, every muscle rippled with perfection. There were no unsightly blemishes. There were no visible sexual organs.

They were human - almost.

They were better than human. They were perfect. And at that moment, I believe, the heart went out of me - and out of so many who were watching.

Of course, those who were not in the room could not smell the newcomers, as I could. The odour was pleasant, not overwhelming. And indescribable. Nothing on Earth had ever smelled like that, and yet - it was perfect. Once one had encountered that scent, one could never imagine being without it.

The Xenans are as good as they are beautiful. They are concerned that their presence disturbs some of us so greatly that - should we not be able to overcome our reaction - we will have to be left behind on a doomed world. For the Xenans know of no worlds which are not already inhabited. By themselves. They are willing to share.

I have said that they know of no other worlds, but this is not quite true. The Xenans have asked me to write this account, bare as it is, for a particular reason. They have discovered another inhabited planet, some distance from here, and are sending a team even now to contact them, for they fear yet another disaster in the making, and the need for yet another rescue attempt. They would rather die than not try to save them. And yet, they fear rejection.

So I am writing this for you, the peoples of another world, whose name I cannot pronounce, and of whose nature I am ignorant. This is my hope for you:

I hope that you are green. That you have six arms, or three eyes each. I hope that you move by flying, or hopping, or that you live under water. I hope that you communicate by grunts, or sign language, or elaborate dance. I hope you have three genders.

I hope, above all, that your sense of beauty, and proportion, is not as ours. For then your rescuers will appear to you as pleasant, though possibly ungainly, beings, who are welcome for the help they offer. And not, as in our case, as a curse.

For I have seen the future - and it is not us. The humans of Earth may be rescued from death, but they will never achieve their potential. For the others will always be there, so lovely, so clever, and so kind....

If I can't stop crying, I can't go. If I can't go, I will mourn for the rest of my life, however short it is. For I will never be able to forget the sight of their faces, the sound of their voices, the kind look in their eyes.

If I tore my own eyes out, I could not.

The Xenans have agreed to send this, along with a photograph of myself, ahead of them. Your need is not so great. It may be possible to save your world without alien interference. You have more time than we did.

Choose wisely, my friends.

Yours,

Rajiv Bhabha,

Secretary General,

The United Nations of the Planet Earth